The overall objective of this proposal is to continue the ongoing Clinical Trial to compare the efficacy of Vitamin A (Retinol) versus a placebo in the prevention of basal cell carcinoma or cutaneous squamous cell carcinoma in participants diagnosed to have multiple actinic keratoses. Our research plan involves a multidisciplinary cancer research effort with the following specific aims: 1) To compare the incidence, frequency and time to development of subsequent basal or squamous cell skin cancers, 2) to measure the incidence, frequency and time to development of other cancers, 3) To determine the frequency of and motivate protocol compliance, 4) To determine the incidence, frequency, type and degree of toxicity.